AM radio receiver with switchable IF bandwidth
AssigneeRobert Bosch GmbH
InventorPeter Braegas
Life of this patent
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Abstract
A method for IF bandwidth switchover and an IF bandwidth switchover apparatus in an AM radio receiver are described. This kind of switchover is appropriate if radio transmitters not only transmit at the normal modulation bandwidth but also broadcast programs with an expanded bandwidth. To obtain optimal reception, the switchover is performed as a function of the reception conditions. To this end, the error rate of supplemental AM information, adjacent-channel interference and the signal strength can be evaluated. These criteria can be used either individually or in various combinations.
Claims21
A method for IF bandwidth switchover in an AM radio receiver for receiving signals from respective transmitters which each modulate and transmit one of a normal narrow-bandwidth signal and an expanded or wide-bandwidth signal, in which the receiver has an adjustable IF filter and the transmitters broadcast supplemental AM information,
- comprising the steps of
- evaluating, in the AM radio receiver, a modulation bandwidth code contained in the supplemental AM information and an error rate of the supplemental AM information, and
- selectively,
- adjusting bandwidth of said IF filter (18) to a wide bandwidth if the modulation bandwidth indicated by said bandwidth code is expanded, and there is a low error rate, and
- adjusting the bandwidth of said IF filter to a narrow bandwidth if the modulation bandwidth indicated by said bandwidth code is expanded, and there is a high error rate.
A method for IF bandwidth switchover in an AM radio receiver for receiving signals from respective transmitters which each modulate and transmit one of a normal narrow-bandwidth signal and an expanded or wide-bandwidth signal, in which the receiver has an adjustable IF filter and the transmitters broadcast supplemental AM information,
- comprising the steps of
- evaluating, in the AM radio receiver, a modulation bandwidth code contained in the supplemental AM information and an adjacent-channel interference signal of the supplemental AM information, and
- selectively,
- adjusting bandwidth of said IF filter (18) to a wide bandwidth if the modulation bandwidth indicated by said bandwidth code is expanded, and there is low adjacent-channel interference, and
- adjusting the bandwidth of said IF filter to a narrow bandwidth if the modulation bandwidth indicated by said bandwidth code is expanded, and there is high adjacent-channel interference.
A method for IF bandwidth switchover in and AM radio receiver for receiving signals from respective transmitters which each modulate and transmit one of a normal narrow-bandwidth signal and an expanded or wide-bandwidth signal, in which the receiver has an adjustable IF filter and the transmitters broadcast supplemental AM information,
- comprising the steps of
- evaluating, in the AM radio receiver, a modulation bandwidth code contained in the supplemental AM information and a signal strength of the AM supplemental information from said transmitter, and
- selectively,
- adjusting bandwidth of said IF filter (18) to a wide bandwidth if the modulation bandwidth indicated by said bandwidth code is expanded, and there is a high signal strength, and
- adjusting the bandwidth of said IF filter to a narrow bandwidth if the modulation bandwidth indicated by said bandwidth code is expanded, and there is a low signal strength.
An IF bandwidth switchover apparatus in an AM radio receiver, for receiving signals from transmitters which each modulate and transmit one of a normal narrow-bandwidth signal and an expanded or wide-bandwidth signal, having
- a decoder (10) for supplemental AM information broadcast by the transmitters, wherein
- a bandwidth decoder (12), for evaluating a modulation bandwidth code contained in the supplemental AM information,
- and an error rate evaluator (14) for the supplemental AM information are provided, and the bandwidth decoder (12) and the error rate evaluator (14) are connected to
- an evaluation and control circuit (16), which sets a reversible IF filter (18) to "wide" if there is the expanded modulation bandwidth combined with a low error rate, and sets the filter to "narrow" if one of the following conditions pertains:
- there is a normal modulation bandwidth, or
- there is the expanded modulation bandwidth combined with a high error rate.
An IF bandwidth switchover apparatus in an AM radio receiver, for receiving signals from transmitters which each modulate and transmit one of a normal narrow-bandwidth signal and an expanded or wide-bandwidth signal, having a decoder (10) for supplemental AM information broadcast by the transmitters, wherein
- a bandwidth decoder (12), for evaluating a modulation bandwidth code contained in the supplemental AM information, and an adjacent-channel interference evaluator (20) are provided, and
- the bandwidth decoder (12) and the adjacent-channel interference evaluator (20) are connected to
- an evaluation and control circuit (16), which sets a reversible IF filter (18) to "wide" if there is the expanded modulation bandwidth combined with slight adjacent-channel interference, and sets the filter to "narrow" if one of the following conditions pertains:
- there is the normal modulation bandwidth, or
- there is the expanded modulation bandwidth combined with high adjacent-channel interference.
The IF bandwidth switchover apparatus of claim 18, wherein
- the adjacent-channel interference evaluator (20) is connected on an output side of the reversible IF filter (18) and the evaluation and control circuit (16) has a switching hysteresis.
An IF bandwidth switchover apparatus in an AM radio receiver, for receiving signals from transmitters which each modulate and transmit one of a normal narrow-bandwidth signal and an expanded or wide-bandwidth signal, having
- a decoder (10) for supplemental AM information broadcast by the transmitters, wherein
- a bandwidth decoder (12), for evaluating a modulation bandwidth code contained in the supplemental AM information,
- and a signal strength meter (22) are provided, and the bandwidth decoder (12) and the signal strength meter (22) are connected to
- an evaluation and control circuit (16), which sets a reversible IF filter (18) to "wide" if there is the expanded modulation bandwidth combined with at least one of high signal strength, and sets the filter to "narrow"
- if there is a normal modulation bandwidth or if there is the expanded modulation bandwidth combined with low signal strength.
Dependencies are inferred from the claim text.